A caramel pigment can be obtained by subjecting an edible carbohydrate such as starch hydrolysate, syrup or saccharide to heat treatment, to heat treatment with an acid or an alkali, to heat treatment with a sulfurous acid compound and/or an ammonium compound, or to heat treatment with said compounds and an additional acid or alkali. The caramel pigment thus obtained is easily dissolved in water and shows blackish brown. A caramel is widely used as a coloring agent for food products, and is adhered on the surface of a food product to color it to improve the commercial value of the processed food product. For processed meat food products such as roasted pork, a sausage, bacon and ham, the caramel pigment is used to color their surfaces, thereby making the appearance of the products better so that they appear delicious and awakes consumers' desire.
In addition to the caramel pigments, there are water-soluble pigments such as cacao pigments, beet pigments, safflower pigments, gardenia pigments, kaoliang pigments and onion pigments, which are used in food products such as processed meat products, processed marine products, beverages and confectionery. Conventionally, in order to apply a water-soluble pigment such as a caramel pigment to the surface of such a processed meat or fish meat product, coloration is carried out by, for example, adhering or spraying the caramel pigment solely or with a liquid sauce to the surface.
However, said coloring method has a defect that a water-soluble pigment such as a caramel pigment may be dissolved in water generated from a food product during cooking or in sauce, and hardly provides a uniformly colored food product.
A pigment transfer sheet for foods using a caramel pigment easily brings stickiness to make blocking. In the process that a food product is wrapped with a sheet or a cylindrical package material having an inner pigment layer, which is filled with the food product, and then transfer of the caramel pigment is performed by cooking with heat, the caramel pigment is dissolved in water from the food and cannot colored uniformly.
Patent Literature 1 (Japanese Patent Laid-Open No. 2005-137282) as described below shows a method in which a vegetable dry powder is added to glutinous rice and rice to produce an edible ink, and the edible ink is printed on a plastics film to transfer it to a food product. While the literature describes that a color is difficult to flow in this invention, in contrast to conventional edible pigments, pigment bleeding hardly occurs because of using the particulate pigment of the vegetable dry powder.
Also, Patent Literature 2 (Japanese Patent Laid-Open No. 2008-143992) as described below relates to an ink for a writing instrument to transfer a pattern or the like on the surface of a food product such as a biscuit. Patent Literature 2 discloses that blocking which easily occurs during preservation is prevented by adding a polyglyceryl fatty acid ester, a vegetable hardened oil or the like to ink composition (containing an edible pigment). However, transferring to the food product can be carried out through pressure-sensitive transfer with a writing instrument such as a ball-point pen, and there is no description of transferring by heating. Furthermore, any combination of the components of the transfer layer of the present application is not described.
Patent Literature 3 (Japanese Patent Laid-Open No. 2000-139401) relates to manufacturing of a pigment transfer film that can be subjected to shirring, wherein an ink composition (containing an edible pigment) is improved to enhance flexibility. After printing, a conventional ink becomes brittle to easily peel off a film. In order to improve said transfer film, a protective layer is further provided via a buffer layer. This allows shirring to be performed easily, but there is no description about the prevention of pigment bleeding.